Biopsy samples from bone tissue are typically collected from a sampling site in a patient by the use of bone biopsy devices. Typical bone biopsy devices include a hollow cannula which surrounds a stylet. The style includes a sharp distal tip which extends distally beyond the tip of the hollow cannula when the stylet is secured within the cannula. The combined cannula and stylet is used to penetrate through the cortex or outer layer of bone so as to sample the softer tissue or marrow within the bone. Once the cannula and stylet have penetrated into the bone, the stylet is removed and the cannula further advanced into the bone to capture a marrow sample.
The architecture of the tissue sample is important in several respects. Initially, the size of the sample is important, with larger sample sizes representing better samples for subsequent testing to be performed on the tissue. The larger the cannula and stylet which is used, however, the more pain is generated at the penetration site for the patient. Another aspect of sampling is minimizing damage to the sample, such as compressive forces, during sampling and removal.
A variety of bone biopsy devices have been proposed to improve the biopsy sampling procedure. Andelin et al. U.S. Pat. No. 6,110,128, Guirtino et al. U.S. Pat. No. 5,615,690 and Mittermeier et al. U.S. Pat. No. 6,063,037 describe a biopsy devices with structural features designed to enhance sample retention. Other bone biopsy devices have been developed which aid in the preservation of sample integrity by virtue of their structure. One such device is described in Krueger et al., U.S. Pat. No. 6, 443,910, which includes a sampling cannula having a “cutting finger” on the distal portion of the cannula.
Difficulty has been encountered in the art in the balancing between the structural requirements of bone biopsy devices and desirable sampling attributes. Providing bone biopsy devices that consistently sample without damaging forces being exerted upon the sample has proven challenging. Furthermore, accommodating patient comfort by reducing the need for multiple site sampling has presented another challenge. Preserving the architecture of the sample during its obtaining and removal presents yet another factor to be balanced in bone biopsy devices.
There is a need in the field of medical bone biopsy devices for biopsy devices which facilitate the retention of the obtained sample while at the same time preserving the structural integrity of the sample and reducing the amount of trauma to the patient.